Method and system of sample edge detection and sample positioning for image inspection apparatus

Abstract

Systems, apparatuses, and methods for detecting a location of a positioned sample may include an electrostatic holder configured to hold a sample and form a gap area between an outside edge of the sample and a structure of the electrostatic holder when the electrostatic holder holds the sample, wherein the gap area is coated with a first coating configured to reflect a first wavelength of light with first brightness and to reflect a second wavelength of the light with second brightness, the first wavelength is within a predetermined range of wavelengths, the second wavelength is outside the predetermined range of wavelengths, and the first brightness is higher than the second brightness; a light source configured to direct the light at the gap area; and an optical detector configured to image the light reflected off the gap area.

The invention claimed is: 
     
         1 . An apparatus for detecting a location of a positioned sample, the apparatus comprising:
 an electrostatic holder configured to hold a sample and form a gap area between an outside edge of the sample and a structure of the electrostatic holder when the electrostatic holder holds the sample, wherein
 the gap area is coated with a first coating configured to reflect a first wavelength of light with first brightness and to reflect a second wavelength of the light with second brightness, 
 the first wavelength is within a predetermined range of wavelengths, 
 the second wavelength is outside the predetermined range of wavelengths, and 
 the first brightness is higher than the second brightness; 
   a light source configured to direct the light at the gap area; and   an optical detector configured to image the light reflected off the gap area.   
     
     
         2 . The apparatus of  claim 1 , further comprising a polarizing beam splitter configured to polarize the light directed at the gap area with a predetermined polarity. 
     
     
         3 . The apparatus of  claim 2 , wherein the first coating is coated with a second coating configured to modify polarization of the light. 
     
     
         4 . The apparatus of  claim 1 , wherein the first wavelength of the light comprises one of a red light, a blue light, or a green light, and the second wavelength of the light comprises another one of the red light, the blue light, or the green light. 
     
     
         5 . The apparatus of  claim 4 , wherein the first wavelength of the light is a blue light, and the second wavelength of the light is a green light or a red light. 
     
     
         6 . The apparatus of  claim 1 , wherein the light comprises a plurality of wavelengths. 
     
     
         7 . The apparatus of  claim 6 , wherein the light comprises a visible light. 
     
     
         8 . The apparatus of  claim 6 , wherein the light comprises a white light. 
     
     
         9 . The apparatus of  claim 1 , wherein the optical detector is further configured to image the light in a plurality of color channels. 
     
     
         10 . The apparatus of  claim 9 , wherein the plurality of color channels comprises a red channel, a green channel, and a blue channel. 
     
     
         11 . The apparatus of  claim 1 , wherein the first coating is further configured to reflect a third wavelength of the light with third brightness, wherein the third wavelength of the light is outside the predetermined range of wavelengths, and the first brightness is higher than the third brightness. 
     
     
         12 . The apparatus of  claim 11 , wherein the optical detector is further configured to:
 image the light reflected off the gap area as a first image in a first color channel, a second image in a second color channel, and a third image in a third color channel, wherein the first wavelength of the light is imaged in the first color channel, the second wavelength of the light is imaged in the second color channel, and the third wavelength of the light is imaged in the third color channel; and wherein   the apparatus further comprises circuitry configured to generate a synthesis image based on the first image, the second image, and the third image.   
     
     
         13 . The apparatus of  claim 12 , wherein the apparatus further comprises circuitry configured to:
 determine a gray level of a pixel based on a first difference and a second difference, wherein
 the first difference is between a first gray level of a first pixel of the first image and a second gray level of a second pixel of the second image, 
 the second difference is between the first gray level of the first pixel of the first image and a third gray level of a third pixel of the third image, and 
 the first pixel, the second pixel, and the third pixel are co-located; and 
   generate the synthesis image based on the gray level of the pixel.   
     
     
         14 . The apparatus of  claim 13 , wherein the apparatus further comprises circuitry configured to:
 determine the gray level of the pixel as a weighted sum of the first difference and the second difference, wherein   the first difference is weighted with a first weight value,   the second difference is weighted with a second weight value, and   the first weight value and the second weight value are in a range between zero and one.   
     
     
         15 . A non-transitory computer-readable medium that stores a set of instructions that is executable by at least one processor of an apparatus to cause the apparatus to perform a method, the method comprising:
 causing the apparatus to obtain light reflected off a gap area formed between an outside edge of a sample held at an electrostatic holder and a structure of the electrostatic holder, wherein
 the gap area is coated with a first coating configured to reflect a first wavelength of light with first brightness, to reflect a second wavelength of the light with second brightness, and to reflect a third wavelength of the light with third brightness, 
 the first wavelength is within a predetermined range of wavelengths, 
 the second wavelength and the third wavelength are outside the predetermined range of wavelengths, and 
 the first brightness is higher than the second brightness and the third brightness; 
   causing the apparatus to image the light as a first image in a first color channel, a second image in a second color channel, and a third image in a third color channel, wherein a first wavelength of the light is imaged in the first color channel, a second wavelength of the light is imaged in the second color channel, and a third wavelength of the light is imaged in the third color channel;   generating a synthesis image based on the first image, the second image, and the third image; and   determining a location of the sample based on the synthesis image.   
     
     
         16 . The non-transitory computer-readable medium of  claim 15 , wherein generating the synthesis image based on the first image, the second image, and the third image comprises:
 determining a gray level of a pixel based on a first difference and a second difference, wherein   the first difference is between a first gray level of a first pixel of the first image and a second gray level of a second pixel of the second image,   the second difference is between the first gray level of the first pixel of the first image and a third gray level of a third pixel of the third image, and   the first pixel, the second pixel, and the third pixel are co-located.   
     
     
         17 . The non-transitory computer-readable medium of  claim 16 , wherein determining the gray level of the pixel based on the first difference and the second difference comprises:
 determining the gray level of the pixel as a weighted sum of the first difference and the second difference, wherein   the first difference is weighted with a first weight value,   the second difference is weighted with a second weight value, and   the first weight value and the second weight value are in a range between zero and one.   
     
     
         18 . The non-transitory computer-readable medium of  claim 15 , wherein the first coating is coated with a second coating configured to modify polarization of the light. 
     
     
         19 . The non-transitory computer-readable medium of  claim 15 , wherein the first wavelength of the light, the second wavelength of the light, and the third wavelength of the light comprise a red light, a blue light, and a green light. 
     
     
         20 . A system, comprising:
 an image inspection apparatus configured to scan a sample positioned on a sample holder and generate an image of the sample;   an electrostatic holder configured to hold a sample and form a gap area between an outside edge of the sample and a structure of the electrostatic holder when the electrostatic holder holds the sample, wherein a surface of the gap area is applied with a mechanical milling process;   a light source configured to direct the light at the gap area with a predetermined polarity; and an optical detector configured to image the light reflected off the gap area.